Monitoring of SF6 Degradation in GIS Using Frequency Response Analysis

Frequency Response Analysis (FRA) is generally used to detect any changes in the active part of the test object. Several studies have analyzed the effect of different mechanical changes including deformations and oil insulation decays on frequency response of transformers as a test object, however noresearch has ever studied the effect of gas degradation on frequency signature of a gas insulated substation (GIS). This paper investigates the possibility of using frequency response analysis to assess the quality of insulation medium in gas insulated substation (GIS). For this purpose, a single phase GIS filled with SF6 between the main conductor and the enclosure is simulated in Maxwell 3D using finite element method to obtain the electrical parameters of the substation in real mode operation. Measurement of frequency response was carried out in GIS simulations with different insulation qualities from healthy to weak condition. The results show that the frequency response of GIS can disclose any minor deterioration in gas quality of the switchgear.